1. Field of the Invention
The present invention relates generally to agents for reducing or preventing the build-up of dental calculus, commonly called tartar, in domestic animals. More particularly, the invention relates to methods and compositions relating to rawhide and other products chewed by animals and coated with a calculus-preventing agent.
2. Description of the Prior Art
Dental calculus, or tartar, is recognized as a recurring calcified deposit on the surfaces of the teeth of domestic animals, including dogs and cats, as well as humans. It is generally recognized that dental calculus develops in a sequential process that involves the accumulation of dental plaque and the subsequent calcification of the plaque by saliva, which has very high concentrations of calcium and phosphate. Although calculus, per se, is not directly responsible for the development of oral diseases, it is recognized as a secondary, or contributing, factor in the development of periodontal disease because: (1) its presence on the teeth serves as a local irritant to the adjacent soft tissues, eliciting an inflammatory response (and soft tissue inflammation is the initial phase of periodontal disease); (2) it interferes with the normal cleansing of the tooth surfaces, which occurs during the mastication of food or through the performance of conventional oral hygiene procedures, such as toothbrushing and flossing; and (3) it harbors bacterial toxins, which exacerbate periodontal disease formation, by virtue of its porosity. Once formed, calculus deposits can only be removed through concerted mechanical procedures, i.e., a dental prophylaxis. Thus, the prevention of dental calculus is of importance not only for cosmetic reasons, but also because of dental calculus' secondary role in the development of periodontal disease, and the resultant systemic infections, alveolar bone recession, tooth loss and adverse mouth/breath odors.
At present, the recognized approaches for the prevention of dental calculus formation are: (1) the meticulous, daily removal of dental plaque prior to its calcification; and (2) the daily application of crystal growth inhibitors that interfere with the calcification of dental plaque by saliva. Known crystal growth inhibitors include various soluble pyrophosphates, sodium tripolyphosphate, soluble diphosphonates, and certain soluble zinc compounds, such as zinc chloride. These crystal growth inhibitors are currently being used in dentifrices and mouthwashes for preventing dental calculus formation in humans. Soluble pyrophosphates are also currently being cooked or baked in the dough of commercially-prepared diets for dogs and cats for the stated purpose of preventing dental calculus formation in these domestic animals.
It has also been reported that sodium hexametaphosphate has been found to be useful in preventing the build up of dental calculus. In U.S. Pat. No. 5,296,217, issued on Mar. 22, 1994, it is disclosed that sodium hexametaphosphate is successful in preventing or reducing calculus build-up when applied as a coating to pet foods.